The use of hydrogen as an alternative fuel source is receiving wide attention in both political and technical arenas. One reason for this attention lies in the ability of hydrogen to burn cleanly without producing any toxic by-products. Hydrogen is a clean and renewable energy resource, not contributing to the greenhouse effect. Biological production of hydrogen using wastewater and other biomass as raw materials has been attracting attention as an environmentally friendly process that does not consume fossil fuels. An area of concern in the use of hydrogen as a fuel source is in developing an efficient, economical method of production in which unwanted coproducts are not produced. Gasification, pyrolysis, and fermentation of biomass have been, and are being considered as potential routes to hydrogen production.
Hydrogen production by microorganisms can be divided into two main categories: one is by photosynthetic bacteria cultured under anaerobic light conditions, and the other is by other anaerobic bacteria. The latter possess the ability to produce hydrogen without photoenergy. There have been many studies on the conversion of biomass to hydrogen by anaerobic bacteria. There have also been studies on the development of hydrogen production during the treatment process of organic wastewater using anaerobic bacteria. Hydrogen production by anaerobic microflora has been reported by Minoda et al and Sykes and Kirsch. In their experiments, hydrogen production resulted from inhibition of methane formation from hydrogen, and microflora which produces hydrogen with high efficiency has not been obtained. In a study by Yoshiyuko Ueno et al, experiments were carried out in order to select the anaerobic microflora suitable for the production of hydrogen with a medium containing cellulose as a model of wastewater.
Plant biomass such as agricultural residues and bioindustrial wastes contains high percentages of cellulose and hemicellulose, and represents one of the most abundant renewable energy sources. On the other hand, little interest has been focused on biologic conversion of cellulosic materials present in biomass to high-value hydrogen. To convert biomass to hydrogen, the full use of pentoses in addition to hexoses in hydrolysates of cellulose and hemicellulose is important. Because Clostridium sp. strain no. 2, isolated from termites, has been found to convert arabinose and xylose to hydrogen more efficiently than glucose, studies led Fumiaki Taguchi et al to investigate direct hydrogen production by a combination procedure in one flask consisting first of enzymatic hydrolysis of cellulose and hemicellulose, and second, hydrogen fermentation of the hydrolysates by strain no. 2.